Whether you see a benefit or not depends upon your driving style: blasting about with your foot on and off the throttle you would see little difference but in a long steady cruise the economy gain is worth having. There is no disadvantage to having it as long as it is set up right.
Another possible advantage (and I'm guessing here!) might be for an engine that tended to
oil up plugs at light throttle and tickover where the extra advance might help to stop this occurring.